I just wanted to contribute to this thread. I am a graduating 3rd year FM Resident this year, and I am also in the Match for EM. I am fully prepared that I may have to repeat all 3 years. This is a little depressing, but I know that it will be well worth it in the end. As has been mentioned above, you may be credited 3-6 months if your lucky, but depending on the program and their need for you to feel a job position as much as a resident position you also may not be. I have found it an advantage in interviewing to be able to say that I will have completed a full GME Residency before I start an ER program and that I am also a licensed physician. But, even with that said, I am not guaranteed a match because, as we all know, ER is very competitive.
In regards to transferring from a PGY1 FM position into an ER program, I have seen from several friend's experiences that this is very difficult to do (even if you have excellent board scores.) Having completed 1 year of internship is not looked at as nearly being as valuable. Not saying that it can't and hasn't been done, but its difficult to do and I'm pretty sure that in most places you won't get much if any credit. It is also very difficult to get out of your current internship program for a substantial enough number of interviews to guarantee a match. This is also true of your 2nd FM year, and by the time you've suffered through 2 years of the Primary Care crap you might as well just finish up the third. The third is usually the easiest year for FM at most program anyways and there is often ample time to interview. Bottom line, for most people, once FM has got its claws in you you won't be escaping for 3 years - at least not easily.
Good Luck.
